scholarly journals The Pristine survey – VII. A cleaner view of the Galactic outer halo using blue horizontal branch stars

2019 ◽  
Vol 490 (4) ◽  
pp. 5757-5769 ◽  
Author(s):  
Else Starkenburg ◽  
Kris Youakim ◽  
Nicolas Martin ◽  
Guillaume Thomas ◽  
David S Aguado ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Narrow Band ◽  
Sloan Digital Sky Survey ◽  
Limiting Factor ◽  
Horizontal Branch ◽  
Complete Sample ◽  
Negative Power ◽  
Horizontal Branch Stars ◽  
Sky Survey ◽  
Clean Sample

ABSTRACT We use the Pristine survey CaHK narrow-band photometry, combined with the Sloan Digital Sky Survey (SDSS)ugr photometry, to provide a cleaner sample of blue horizontal branch stars in the Galactic halo out to large distances. We demonstrate a completeness of 91 per cent and a purity of 93 per cent with respect to available spectroscopic classifications. We subsequently use our new clean sample of these standard candles to investigate the substructure in the Galactic halo over the Pristine footprint. Among other features, this allows for a careful tracing of multiple parts of the Sagittarius stream, providing a measurement independent from other tracers used and reaching larger distances. Moreover, we demonstrate with this clean and complete sample that the halo follows a density profile with a negative power-law slope of 3.5–4.0. As the relatively shallow SDSS u band is the limiting factor in this technique, we foresee large potential for combining Pristine survey photometry with the much deeper u-band photometry from the Canada–France–Imaging Survey.

scholarly journals Blue Horizontal-Branch Stars in the Sloan Digital Sky Survey. II. Kinematics of the Galactic Halo

2004 ◽  
Vol 127 (2) ◽  
pp. 914-924 ◽  
Author(s):  
Edwin Sirko ◽  
Jeremy Goodman ◽  
Gillian R. Knapp ◽  
Jon Brinkmann ◽  
eljko Ivezi ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Sky Survey

Blue Horizontal-Branch Stars in the Sloan Digital Sky Survey. I. Sample Selection and Structure in the Galactic Halo

2004 ◽  
Vol 127 (2) ◽  
pp. 899-913 ◽  
Author(s):  
Edwin Sirko ◽  
Jeremy Goodman ◽  
Gillian R. Knapp ◽  
Jon Brinkmann ◽  
eljko Ivezi ◽  
...  
Keyword(s):  
Galactic Halo ◽  
Sample Selection ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Horizontal Branch Stars ◽  
Sky Survey

scholarly journals Contribution of Gaia Sausage to the Galactic Stellar Halo Revealed by K Giants and Blue Horizontal Branch Stars from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope, Sloan Digital Sky Survey, and Gaia

2022 ◽  
Vol 924 (1) ◽  
pp. 23
Author(s):  
Wenbo Wu ◽  
Gang Zhao ◽  
Xiang-Xiang Xue ◽  
Sarah A. Bird ◽  
Chengqun Yang
Keyword(s):  
Gaussian Mixture ◽  
Sloan Digital Sky Survey ◽  
Horizontal Branch ◽  
Integrals Of Motion ◽  
Eccentric Orbits ◽  
Horizontal Branch Stars ◽  
Sky Survey ◽  
Stellar Halo ◽  
The Mean ◽  
K Giants

Abstract We explore the contribution of the Gaia Sausage to the stellar halo of the Milky Way by making use of a Gaussian mixture model (GMM) and applying it to halo star samples of Large Sky Area Multi-Object Fiber Spectroscopic Telescope K giants, Sloan Extension for Galactic Understanding and Exploration K giants, and Sloan Digital Sky Survey blue horizontal branch stars. The GMM divides the stellar halo into two parts, of which one represents a more metal-rich and highly radially biased component associated with an ancient, head-on collision referred to as the Gaia Sausage, and the other one is a more metal-poor and isotropic halo. A symmetric bimodal Gaussian is used to describe the distribution of spherical velocity of the Gaia Sausage, and we find that the mean absolute radial velocity of the two lobes decreases with the Galactocentric radius. We find that the Gaia Sausage contributes about 41%–74% of the inner (Galactocentric radius r gc < 30 kpc) stellar halo. The fraction of stars of the Gaia Sausage starts to decline beyond r gc ∼ 25–30 kpc, and the outer halo is found to be significantly less influenced by the Gaia Sausage than the inner halo. After the removal of halo substructures found by integrals of motion, the contribution of the Gaia Sausage falls slightly within r gc ∼ 25 kpc but is still as high as 30%–63%. Finally, we select several possible Sausage-related substructures consisting of stars on highly eccentric orbits. The GMM/Sausage component agrees well with the selected substructure stars in their chemodynamical properties, which increases our confidence in the reliability of the GMM fits.

scholarly journals Stars in the Galactic Halo

1995 ◽  
Vol 164 ◽  
pp. 75-83
Author(s):  
T.D. Kinman
Keyword(s):  
Globular Clusters ◽  
Galactic Halo ◽  
Horizontal Branch ◽  
Field Star ◽  
Horizontal Branch Stars

The field star halo is comprised of those field stars that are like the stars found in the halo globular clusters. We discuss the halo properties — in particular whether Vrot is a function of z. An analysis of recent surveys for blue horizontal branch stars is described; the halo that is defined by these stars is composite and contains both a spherical and flat component.

scholarly journals The Distribution of Field Horizontal–Branch Stars in the Galactic Halo

1977 ◽  
Vol 4 (2) ◽  
pp. 73-74
Author(s):  
A. G. Davis Philip
Keyword(s):  
Density Distribution ◽  
Galactic Halo ◽  
Galactic Plane ◽  
Horizontal Branch ◽  
Schmidt Telescope ◽  
Rr Lyrae Stars ◽  
Rr Lyrae ◽  
Horizontal Branch Stars ◽  
General Program ◽  
Objective Prism

Since the time allowed per paper at this joint discussion is short only one aspect of the stellar distribution at high galactic latitudes will be presented here, namely the distribution of field horizontal-branch stars (FHB) in the galactic halo. First, the method by which FHB stars are found will be described. Second, the density distribution of FHB stars will be compared with that of the RR Lyrae stars.As part of a general program to study the stellar density distribution perpendicular to the galactic plane a number of possible FHB stars has been discovered. In each survey area objective prism plates (at a dispersion of 280 Å/mm. to a limiting magnitude of V = 14) are taken with the Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory or the Schmidt telescope at the Warner and Swasey Observatory. A set of direct plates are taken also to obtain photographic magnitudes for the stars with spectral classifications.

scholarly journals The Hubble Sequence at z ∼ 0 in the IllustrisTNG simulation with deep learning

2019 ◽  
Vol 489 (2) ◽  
pp. 1859-1879 ◽  
Author(s):  
Marc Huertas-Company ◽  
Vicente Rodriguez-Gomez ◽  
Dylan Nelson ◽  
Annalisa Pillepich ◽  
Connor Bottrell ◽  
...  
Keyword(s):  
Neural Network ◽  
Morphological Type ◽  
Sloan Digital Sky Survey ◽  
High Mass ◽  
Complete Sample ◽  
Hubble Sequence ◽  
Sky Survey ◽  
Mass Size ◽  
S0 Galaxies ◽  
Mass Functions

ABSTRACT We analyse the optical morphologies of galaxies in the IllustrisTNG simulation at z ∼ 0 with a convolutional neural network trained on visual morphologies in the Sloan Digital Sky Survey. We generate mock SDSS images of a mass complete sample of $\sim 12\, 000$ galaxies in the simulation using the radiative transfer code SKIRT and include PSF and noise to match the SDSS r-band properties. The images are then processed through the exact same neural network used to estimate SDSS morphologies to classify simulated galaxies in four morphological classes (E, S0/a, Sab, Scd). The CNN model classifies simulated galaxies in one of the four main classes with the same uncertainty as for observed galaxies. The mass–size relations of the simulated galaxies divided by morphological type also reproduce well the slope and the normalization of observed relations which confirms a reasonable diversity of optical morphologies in the TNG suite. However we find a weak correlation between optical morphology and Sersic index in the TNG suite as opposed to SDSS which might require further investigation. The stellar mass functions (SMFs) decomposed into different morphologies still show some discrepancies with observations especially at the high-mass end. We find an overabundance of late-type galaxies ($\sim 50{{\ \rm per\ cent}}$ versus $\sim 20{{\ \rm per\ cent}}$) at the high-mass end [log(M*/M⊙) > 11] of the SMF as compared to observations according to the CNN classifications and a lack of S0 galaxies ($\sim 20{{\ \rm per\ cent}}$ versus $\sim 40{{\ \rm per\ cent}}$) at intermediate masses. This work highlights the importance of detailed comparisons between observations and simulations in comparable conditions.

scholarly journals Spectral Characteristics of A-Type Stars in the Galactic Halo

1993 ◽  
Vol 138 ◽  
pp. 432-436
Author(s):  
C.J. Corbally ◽  
R.O. Gray
Keyword(s):  
Galactic Halo ◽  
Spectral Characteristics ◽  
Horizontal Branch ◽  
Dwarf Stars ◽  
Horizontal Branch Stars

AbstractAmong 67 early A-type stars at high galactic latitudes, selected to have both small m1 and large c1 Strömgren photometric indices, we find about one third to have quite normal dwarf or subgiant spectra at MK classification dispersion. Those stars with peculiarities included 10 new λ Bootis stars, though none of these appeared significantly evolved. We wonder whether some of the metal-weak dwarf stars in our set may be field horizontal-branch equivalents of the blue, downward-curving, low-luminosity end of the blue horizontal-branch stars.

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